1. Field of the Invention
The present invention relates to an engine having a compression ratio variable device and varies a compression ratio of a combustion chamber depending on the operating condition of an engine to improve the combustion efficiency and reduce the noise/vibration.
2. Description of Related Art
Generally, if the compression ratio is increased, the heat efficiency of engine is improved, and if the ignition timing is advanced to a predetermined level in an ignition type engine, the heat efficiency is increased.
However, if the ignition timing is advanced in a high compression ratio, the fuel is abnormally combusted in a cylinder to damage the engine, and therefore there is a limit in advancing the ignition timing and the output power can be deteriorated thereby.
A variable compression ratio (VCR) device varies the compression ratio of air/fuel mixture in a cylinder depending on the driving condition of an engine.
In an engine having a compression ratio variable device, the compression ratio of the air/fuel mixture is increased in a low load condition of an engine to improve the fuel consumption efficiency, and the compression ratio of the air/fuel mixture is decreased in a high load condition of an engine to prevent the knocking and improve the output of the engine.
The engine having a conventional compression ratio variable device varies the length between a piston and a crank pin that connect the piston with a crankshaft to vary the compression ratio.
The engine having the above type of compression ratio variable device includes a control shaft, a shaft cap, a block cover, and a control motor, wherein the control motor rotates the control shaft and an operating arm that is disposed on the control shaft rotates an eccentric bearing through a link structure.
Meanwhile, a shaft cap is to be used to fix the control shaft on an engine block and a block cover covers the shaft cap and the control shaft, and therefore the number of the components and the weight thereof has to be increased. Further, a control motor as an actuator is disposed at one end portion of the block cover, and therefore the layout volume is increased and the driving torque of the control motor is not effectively transferred to the control shaft.
The information disclosed in this Background of the invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.